The present invention relates to optical sensors for pointing devices, such as mice and trackballs. In particular, it relates to the reduction of the number of components.
Typically, mice and trackballs have a ball which is either rolled across a desktop when a user moves the mouse, or is manipulated with a user's finger for a trackball. This motion is detected in both the x and y directions by the use of two rollers which are biased against the ball inside the device. The rollers are offset from each other at an angle of 90.degree.. Each roller will typically have a shaft connected to an encoder wheel, which is a wheel with a number of slots. A light emitter, such as a light emitting diode (LED) is mounted on one side of each encoder wheel, with one or more photodetectors on the other side. Multiple photodetectors may be used for differential detection. When the encoder wheel turns, light alternately passes through the slots, and is blocked by the encoder wheel, allowing a determination of the amount of movement of the ball in the x or y direction.
Newer mice and track balls will sometimes include a separate roller wheel which the user can manipulate for scrolling. Such a roller wheel is typically also connected to a separate encoder wheel, which also has an emitter and a detector on either side for determining its movement.
Another typical input for mice and trackballs is one or more buttons to indicate a clicking function. The buttons are typically spring biased to allow the user to depress them, and then have them pop back up. The buttons will typically depress a microswitch mounted beneath the button to provide an input signal. Each button typically has its own microswitch.
One of the challenges in the design of such pointing devices is the reduction of costs and reductions in size, or fitting additional functionality in the same size device. One obvious way to reduce costs is to reduce the number of components required to build the mouse or trackball or other pointing device.